Mr Due said: "We are looking very seriously at every individual case, and based on our information it's very likely that children living in reception centres in Norway have been and are being subjected to sexual abuse.

"But generally there is low criminal activity in and around the reception centres."

Last year, more than 31,000 people applied for asylum in Norway of whom 5,300 were unaccompanied children.

Meanwhile, more than a dozen people suspected of planning an attack on an asylum seeker's centre near the Swedish capital Stockholm, have been arrested by police.

The 14 men detained are reported as being Polish, and possibly members of right-wing groups.

Video:2015: Sweden's Migrants Dilemma

The arrests come amid growing opposition in Sweden to migrants and reports of attacks against refugee centres.

The country has been a top European destination for asylum seekers, with 163,000 arrivals last year.

Previously known for its liberal immigration policies welcoming refugees fleeing war and persecution, the Social Democratic-led government changed its stance late last year tightening border controls and immigration regulations.

The International Organization for Migration has announced more than 400 people have already died this year trying to cross the Mediterranean and reach Europe.

It also said migrant crossings in the first six weeks of 2016 are running at nearly 10 times the rate for the same period last year.